It is known to produce an acoustic protection cover for encapsulating a motor vehicle component, the cover including:
a shell based on injection-molded material, the material including a thermoplastic matrix and a filler that is dispersed in such a way as to exhibit a density of between 1.3 and 1.6 a/cm3, the shell including two half-shells delimited by a thin region originating from the molding and forming a flexible hinge,
a layer of foam—in particular polyurethane—elastically compressible overmolding the internal face of the shell, so that the cover forms an insulation system of the “mass-spring” type, the mass being formed by the shell and the spring by the layer,
a manner of holding said half-shells together once the hinge has been folded, so as to allow said component to be encapsulated.
The components able to be encapsulated by such a cover are, for example, power steering or fuel injection pumps.
The thermoplastic matrix used is generally a polyolefin elastomer or a plastomer.
Because of this, its own density is rather low—about 0.85+−0.05—which requires the use of a high level of filling—generally about 60% by mass of the material of the shell—in order to reach the expected density.
The charge used is in particular mineral—being for example in the form of calcite or baryte—or metal.
With such a high level of filling, the extending of the material is very limited, which makes the hinge very brittle.